Method of making butt-welded tubes



Oct. 23, 1934. M. C.SUMMERS 1,978,235

METHOD OF MAKING BUT-T WELDED TUBES Filed Sept. 21, 1933 .Patented Oct.23, 1934 UNITED STATES PATENT OFFICE 1,978,235 METHOD OF MAKINGBUTT-WELDED TUBES Myron (lsSum mers, Warren, Ohio Application September21, 1933, Serial No. 690,434

7 Claims.

The invention relates to the butt-welding of tubes and more particularlyto methods of making tubes from strip metal formed to tubular shape andprovided with butt-welded joints, and

of making steel tubes from strip metal formed to tubular shape andprovided with copper-buttwelded joints.

It is known that steel pieces may be welded together by applying copperat a joint between 10 the pieces and heating the same to beyond themelting point of copper, in a hydrogen atmosphere, so that some of thecopper goes into solid solution in the steel, and some of the iron isdissolved by the copper to produce an integral copper-iron alloy bond orweld, which under desired conditions comprises approximately 97% ironand 3% copper with no free copper present. It is likewise known thatsuch copper welds are actually stronger than the steel itself.

v It has heretofore been proposed to braze the abutting edges of tubesfor use as umbrella sticks by forming a tube from strip metal with aslit, and by forcing a brass wire, coated with flux, in place in theslit, after which the tube is heated until the brass flows and forms abrazed joint.

A satisfactory brazed joint suitable for use in umbrella sticks canpossibly be made in this manner, but in carrying out such a method thebrass wire utilized for forming the brazed joint must be relativelythickso that it will have suflicient inherent strength that it may beforced into the slit in the tube; with the result that when the brazedjoint is formed, a large amount of free copper is present in the brazedjoint, which free copper and therefore the joint, is much weaker thanthe tube thereby formed. Moreover, such a brazed joint is materiallyweaker than the copper welded joint described above.

Accordingly, such brazed tubes with weak joints 40 cannot be safely usedfor the piping of fluids under pressure, as for instance for hydraulicbrake lines, refrigeration system lines, and the like.

- It has also been proposed that tubes may be made by forming a sheetmetal tube blank with edges abutting, by then laying a copper wirewithin the tube blank adjacent to the abutting edges and by thereafterheating the blank and wire to the melting point of copper whereby themolten copper flows into the space between the abutting edges. However,while some satisfactory joints may be made in this manner under idealprecision conditions, yet the proposed making of tubes'in this way isvery expensive because the tube blank is proposed to be initiallywrapped with an asbestos tape or confined within a refractory materialmold for holding the abutting edges of the tube blank together, or forpreventing the same from separating during the subsequent heatingoperation.

Moreover, all of the tubes made in this manner must have their abuttingedges located on the bottom side thereof during the heating operation,for otherwise the copper from the wire laid adjacent to the abuttingedges will not flow between the abutting edges when melted. Likewise,the tube blanks must be maintained substantially level during theheating operation, for otherwise the resulting joint will not beuniform, but the copper will flow to one or another end of the tube whenmolten. And finally, the heating operation per se, is very expensivebecause of the fact that the tube blanks are confined within either arefractory mold or an asbestos tape wrapping.

Accordingly, such a method of making tubes is impractical because of theexcessive expense occasioned'by the necessity for wrapping andunwrapping, or molding and stripping the tube blanks; the necessityofspecially locating and levelling the tube blanks during the heatingoperation; and because of the excessive amount of heat required forcarrying out the heating operation.

The present invention contemplates the making of tubes with butt-weldedjoints, which joints are as strong or stronger than the tube metalitself, as distinguished from weaker brazed joints, while avoiding thedifficulties and. expense encountered in carrying out the heretoforeproposed methods of making tubing just described.

Thus, while copper-butt-welded joints per se, first described above, areknown to havegreat strength, no method has heretofore been known bywhich a. uniformly strong copper-butt-welded joint could be incorporatedin a satisfactory and K inexpensive manner in a tube formed from stripmetal.

I have discovered that a very uniform, strong and efficientcopper-butt-welded joint may be provided in a tube formed from stripmetal if certain conditions are controlled and coordinated in the propermanner.

First, a very small amount only of copper or the bonding material mustbe utilized in order that there will be practically no free copperpresent in the co'pper-butt-welded joint, which if present would weakenthe same.

Second, the small amount of copper or bonding material for forming thecopper-butt-welded joint must be heldin place between the adjacent tubeblank edges which are to be welded without the occurrence of a spreadingaction between the tube blank edges during the heating operation;without requiring the tube to be specially positioned with regard to theadjacent tube blank edges; and without requiring the tube to be levelduring the heating operation.

And third, the heating operation must be carried out with such aco-ordination between the time and temperature of heating that nospreading occurs between the adjacent blank edges during the heatingoperation.

More particularly, I have discovered that these conditions may becontrolled and coordinated by pinching, clamping or otherwise gripping athin copper or bonding material strip or wire between the abutting edgesof the tube blank as the tube blank is formed, and by then quicklyheating the tube blank to a temperature of 1950 F. and upwards for apure copper bonding material buttweld in a steel tube for a very shortperiod of time. In this manner, the required small amount of copper orbonding material may be utilized,

and the copper or bonding material will be held in place and nospreading will occur between the tube blank edges during the heatingoperation.

Accordingly, it is a further object of the present invention to utilizein a method of making a tube with a butt-welded joint or acopper-butt-welded joint, the step of inserting a copper or bondingmaterial strip between the edges of a tube strip as the tube strip isbeing formed to have a tubular shape, and clamping the copper or bondingmaterial strip between the abutting edges of the tube strip during theforming operation so that the formed tube blank per se securely holdsthe copper or bonding material strip in fixed position between itsabutting edges.

It is likewise an object of the present invention to control the heatingoperation so that a spreading does not occur between the tube blankedges during the heating operation, and so that the copper or bondingmaterial strip remains securely clamped between the abutting tube blankedges during the heating operation until the butt-weld ed joint has beenformed.

These and other objects may be obtained by the improved methods andsteps thereof described herein in detail and claimed, and which areshown more or less diagrammatically in the accompanying drawing, inwhich,--

Figure 1 is a diagrammatic plan view of a steel strip from which theimproved copper-butt-welded steel tubes may be made;

Fig. 2 is a sectional view taken on the line 22, Fig. 1;

Fig. 3 is a diagrammatic plan view of a portion of the steel strip shownin Fig. 1 passing through rolls for being formed to a tubular shape, andshowing a thin wire being fed to and clamped between the abutting edgesof the strip;

Fig. 4 is a greatly enlarged fragmentary sectional view taken on theline 44, Fig. 3;

Fig. 5 is a fragmentary sectional view similar to Fig. 4, taken on theline 55, Fig. 3;

Fig. 6 is a fragmentary view similar to Fig. 5, showing a copper stripclamped between the abutting edges of the tube blank;

1,978,286 I In carrying out the improved tube butt-welding method formaking copper-butt-welded steel tubes, a strip indicateddiagrammatically at 9 in Figs. 1 and 2, which may be a steel strip, or astrip slit from a steel sheet or stripsheet, is passed through a tubeforming machine, which may be a usual type of continuous tube rollingmachine indicated diagrammatically at 10 in Fig. 3. The strip 9 inpassing through the tube forming rolls 10 is formed to have a tubularshape, as indicated generally at 11 in Fig. 3, and the free edges 12 ofthe strip 9 are brought up to adjacent alignment with each other.

Up to this point, the steps in making the tubing are merely the commonpractice of forming or making tubes; and the present improved methodthen departs from the usual practice, by provid ing for introducing asmall copper or bonding material wire 13 between the edges 12 of thestrip 9 just as the edges 12 are being brought into adjacent alignment,as at the place 14 indicated more or less diagrammatically in Fig. 3 andas shown in Fig. 4.

At this place, the space 15 between the strip edges 12 is sufficient toaccommodate the copper wire, but as the tube 11 continues to passthrough the forming rolls 10, the edges 12 are pressed more closelytogether so that the copper wire 13 is compressed, pinched, squeezed, orotherwise securely clamped or retained between the edges 12 of the steelstrip 9 and thereby held securely in place. The clamping or squeezing ofthe copper wire 13 so distorts or spreads the wire that the same maytake the general form of a strip indicated diagrammatically at 13a inFig. 5, which strip 13a is securely clamped between the edges 12 of thesteel strip 9, from which the tube 11 is formed.

Thus, if the copper wire 13 had not been introduced between the edges 12of the steel strip 9, the said edges 12 would have been brought intoaligned abutting and pressing contact; but because the wire isintroduced between the free edges 12 of the strip 9 as the tube 11 isformed, the copper wire 13 is compressed, clamped, pinched or otherwisesecurely held or retained between the edges 12 of the strip 9 from whichthe tube 11 is formed.

It may be desirable to utilize copper or bonding material strips ratherthan copper wire, and in such event, a copper strip 13' is fed betweenthe edges 12 of the strip 9 as the strip is passing through the formingmachine 10 so that the thin copper strip 13 as shown in Fig. 6, issecurely clamped, pinched, squeezed or otherwise held securely in placebetween the adjacent edges 12 of the strip 9 formed to make the tube 11.When a copper strip is used as shown in Fig. 6, there may only be a veryslight distortion or compression of the same, as indicated at 13c, butsome distortion or compression of the same does occur in order that thecopper strip is securely held in fixed position between the edges 12 ofthe tube blank.

Of course, the size of the copper or bonding material wire 13, or thethickness of the copper strip 13' may be varied in accordance with thedesired wall thickness of the tube 11 and therefore the thickness of thestrip 9, so that the correct amount of copper is present forsatisfactorily forming a true copper-butt-welded joint. However, byfeeding the copper strip between the free edges 12 of the strip 9 as thetube 11 is being formed, and securely pinching, compressing and holdingthe same between the free 1,978,286. was. the exact amountbrc'opper "or,bonding. I {material 1 necessary for making 3 a; true welded i int maybe jprovided,whlch in fact is only a.

verysmalla'mount of copper or bonding material.

" For 'examplaifa one-half. inch-- maybe used. Q

,The formed tube'll with a copper'br bonding material strip 13a or 13apinched between the known as a continuous bright annealing furnace.

The furnace temperature is maintained at such I a degree that the copperstrip is quickly heated to a temperature of 1950 F. and upwards, whenthe edges of the tube are bonded'together by a copper-Butt we l dedjoint. I have discovered that if the tube is quivkly heated to atemperature of 1950 F. and upwards-no spreading occurs between the edges12 of the formed tube 11, and the copper strip 13a or 13a is thereforeheld in position between the tube edges 12 until a satisfactory anduniform copper-butt-welded joint has been formed.

Thus, when the tube is heated quickly to 1950 F. and upwards, thestrains which may be present in the outer skin or region of the stripmetal 9, in consequence of the forming thereof to tubular shape, arebelieved to be relieved, before relief of the strains present in theinner skin or regions of the tubularly formed strip, due to thetemperature difference between the outer and inner regions of the strip.

The relief of the strains in the outer regions of the formed tube doesnot, however, cause a spreading action to occur between the edges 12,and because of this fact, and of the fact that there is a lag in thetime when the strains are relieved in the inner regions of the tubewalls, during which time lag the alloy in the buttwelded joint begins toform, no spreading action occurs between the edges 12.

It is, however,possible to utilize temperatures above 1950 F., providedthat thetube is quickly heated to the maximum temperature.

For example, if a one-half inch outside diameter steel tube having awall thickness of 0.035 inches and having either a 0.0005 to 0.005 inchcopper wire, or a 0.0005 to a 0.002 inch strip compressed between itsadjacent aligned edges, is quickly heated to a temperature of 1950 F.and upwards in a preferably reducing atmosphere, the copper or bondingmaterial strip is satisfactorily held by the tube in correct positionand a uniform and satisfactory copper-buttwelded joint is formed.

If the size of the tube is varied without changing its wall thickness,approximately the same conditions as to copper or bonding material stripsize, heating temperatureand time of heating are maintained. If the wallthickness of the tube is increased or decreased, the amount of copper orbonding material may be increased or decreased accordingly.

In addition, if the wall thickness is increased, the time of heating orthe heating temperature may be slightly increased accordingly from thosegiven in the examples herein.

'After the heating operation has been performed, the tube is cooled andthe finished tube is shown in Fig. '1 with a copperbutt-welded seam orjoint shown in Figs. 7 and 8 is therelbyproduced.

.It is pointed out that it is neither necessary nor desirable to use anyflux in connection with according to the improved method of making steeltubes when a reducing atmosphere is utilized; although it may benecessary to use some flux if merely a non-oxidizing atmosphere is used.

By carrying out the method of making steel tubes set forth herein, theseam or joint 17 is a true copper weld in which some of the copper goesinto solution in the steel and some of the iron from the steel isdissolved by the copper to produce an integral copper-iron alloy bond,which under desired conditions with a proper amount of copper originallyused, comprises approximately 97 per cent iron and 3 per cent copperwith no free copper present; and such a weld, bond, seam or joint istermed herein a copper-butt-welded. joint, as distinguished from abrazed joint, which is one in which material excess of copper is byintention or necessity initially used with the result that a materialamount of free copper is present in the resulting joint, therebymaterially weakening the joint.

The heating operation has been described as being carried out in abright annealing furnace, which as stated, is preferably of a continuoustype and may for example be a sixty foot furnace with entrance rolls, aheating zone and a cooling zone through which formed tubes maycontinuously pass.

making the copper-butt-welded seam or joint 4 The heating zone in such afurnace is preferably approximately twelve feet long and the tubes beingwelded are continuously passed through the heating zone preferably at aspeed of approximately four feet per minute so that any portion of anytube, is, under the conditions given in the above examples, heated to atemperature of 1950 F. and upwards.

By making a tube in this manner, the copperbutt-welded joint thereof isas strong or stronger than the steel itself and may be subjected tobending, forming, drawing and flaring. Moreover, since the heatingoperation is carried out in a bright annealing furnace under apreferably reducing atmosphere, a dead soft bright annealed tuberesults, which may be galvanized, tinned, or provided with a bakedenamel or porcelain enamel coating Without pickling. Moreover, the tubesmay be directly copper or nickel or chromium plated, or soldered,without performing any special operations thereupon.

Such tubes may be used as conduit for electrical wiring, forrefrigeration system lines, for motor vehicle gasoline, hydraulic brakeand oil lines, for steering columns for automobiles and motor boats, orfor any other purposes for which tubing is used. If it is desired thatthe tubes be hardened or stiffened, the dead soft tubes may be given aslight draw.

In the description of the invention, copper has been referred to, but itis clear that either brass or bronze or silver solder wire or strips,each of which contains copper, may be used in place of copper; so thatwhen the term copper is used herein and in the appended claims, the sameis intended to include copper and copper bearing alloys.

In the event that brass or bronze or silver solder is utilized, the timeand temperature of the heating operation must be varied accordwhat lowerthan that of pure copper; but in any event, the temperature maintainedis one about the melting point of the bonding ma-- terial, whether it becopper, brass, bronze or silver solder. Likewise, the bonding material,whether it be copper, brass, bronze, silver solder or the like, has alower melting point than that of the strip metal from which the tube isformed.

Likewise, copper wires or strips are referred to generically herein andin the appended claims as copper strips, because, while a copper wire orstrip of any shape may be initially fed between the edges of the steelstrip when the same is being formed, the copper wire or strip iscompressed to have generally a strip formation, as indicated at 13a and13a in Figs. 5 and 6 of the drawing.

Moreover, under certain conditions, a copper paste may be applied to theedges 12 of the strip before or during the forming of the tube, so thatthe copper particles in the paste are pinched or compressed between thetube edges when formed and during heating to produce a copperbutt-weldedsteel tube.

And finally, when the term steel strips is used herein, the same isintended to include ordinary steels, alloy steels, stainless steels andother similar metals with which a butt-welded joint may be formed.

Likewise, it is clear that a tube may be made from non-ferrous stripmetal with a welded joint according to the improved method-by utilizinga bonding material having a lower melting point than that of the tubestrip; as for instance by making the tube from a strip of non-ferrousmetal such as brass comprising say 85 per cent copper and 15 per centzinc and pinching between its two edges while being formed, a strip ofsilver solder, a silver wire, or a strip of a suitable alloy such as ahigh zinc brass, which have a lower melting point than the tube strip,and then heating the same quickly to a welding temperature to form abutt-welded joint.

I'claimz- 1. The method of making a copper-butt-welded steel tube, whichincludes forming a tube from a steel strip to bring its free edges intoadjacent alignment, pinching a copper strip between said adjacent edgeswhile forming the tube, and then heating the formed tube quickly in anon-oxidizing atmosphere to 1 950 F. and upwards to form acopper-butt-welded seam between said tube edges without relieving thepinch of the tube edges upon said copper strip.

2. The method of making a copper-butt-welded steel tube which includesforming a tube from a steel strip to bring its free edges into adjacentalignment and at the same time compressing a copper strip between saidadjacent edges, and

then heating the formed tube quickly in a reducing atmosphere to 1950 F.and upwards to form a copper-butt-welded seam between said tube edgeswithout relieving the hold of the tube edges upon said copper strip.

3. The method of making a copper-butt-welded steel tube which includesforming a tube from a steel strip to bring its free edges into adjacentalignment, feeding a copper wire between said adjacent edges andcompressing the wire to flatten and pinch the same between said adjacentedges while forming the tube, and then heating the formed tube quicklyin a reducing atmosphere to 1950 F. and upwards to form acopper-buttwelded seam between said tube edges withoutrelieving the holdof the tube edges upon said fiattened copper wire.

4. In a method of making a copper-butt-welded steel tube formed from asteel strip, the steps of inserting a copper strip between the edges ofthe steel strip as the steel strip is being formed to tubular shape,pinching the copper strip between the steel strip edges during theforming operation so that the formed tube per se securely holds thecopper strip in fixed position between its edges, and then heating theformed tube to form a copper-butt-welded joint between its edges.

5. The method of continuously making a copper-butt-welded steel tubewhich includes continuously forming a tube from a steel strip to bringits free edges into adjacent alignment, pinching copper between saidadjacent edges while forming the tube, and then continuously heating theformed tube quickly in a reducing atmosphere while retaining said copperin position between said edges until fusion takes place to form acopper-butt-welded seam between said tube edges.

6. In a method of making a butt-welded tube formed from a metal strip,the steps of inserting a strip of bonding. material having a lowermelting point than the tube strip between the edges of the tube strip asthe tube strip is being formed to tubular shape, pinching the bondingstrip between the tube strip edges during the forming operation so thatthe formed tube per se securely holds the bonding strip in fixedposition between its edges, and then heating the formed tube to form abutt-welded joint between its edges.

7. A method of continuously making a buttwelded tube, which includescontinuously forming a tube from strip metal to bring its free edgesinto adjacent alignment, pinching a bonding strip having a lower meltingpoint than the tube strip between said adjacent edges while forming thetube, and then continuously heating the formed tube quickly in areducing atmosphere while retaining said bonding strip in positionbetween said tube edges until fusion takes place to formabutt-weldedseam between said tube edges.

MYRON C. SUMMERS.

